U.S. patent number 4,554,152 [Application Number 06/500,070] was granted by the patent office on 1985-11-19 for method of preparing active magnesium-hydride or magnesium hydrogen-storer systems.
This patent grant is currently assigned to Studiengesellschaft Kohle mbH. Invention is credited to Borislav Bogdanovic.
United States Patent |
4,554,152 |
Bogdanovic |
November 19, 1985 |
**Please see images for:
( Certificate of Correction ) ** |
Method of preparing active magnesium-hydride or magnesium
hydrogen-storer systems
Abstract
A method of preparing an active magnesium-hydride or magnesium
hydrogen-storer system which can reversibly take up H.sub.2,
comprising contacting finely divided magnesium hydride or metallic
magnesium with a solution of a metal complex or of a metal-organic
compound of a transition metal of Subgroups IV-VIII of the periodic
table, and then removing the solution. The product performs better
with regard to speed and efficiency upon repeated hydrogenation and
dehydrogenation, as in hydrogen storage and evolution.
Inventors: |
Bogdanovic; Borislav (Mulheim,
DE) |
Assignee: |
Studiengesellschaft Kohle mbH
(Mulheim, DE)
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Family
ID: |
25773749 |
Appl.
No.: |
06/500,070 |
Filed: |
June 1, 1983 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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433078 |
Oct 6, 1982 |
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187907 |
Sep 17, 1980 |
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8739 |
Feb 2, 1979 |
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Foreign Application Priority Data
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Dec 22, 1982 [DE] |
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3247360 |
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Current U.S.
Class: |
423/647; 420/900;
423/644 |
Current CPC
Class: |
C01B
3/0026 (20130101); C01B 3/0078 (20130101); Y02E
60/32 (20130101); Y02E 60/327 (20130101); Y10S
420/90 (20130101) |
Current International
Class: |
C01B
3/00 (20060101); C01B 006/04 () |
Field of
Search: |
;423/647,648R
;420/900 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Ashby et al., "J. of American Chem. Soc.", vol. 99, 1977, pp.
310-311..
|
Primary Examiner: Carter; H. T.
Attorney, Agent or Firm: Sprung Horn Kramer & Woods
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a continuation-in-part application of patent
application Ser. No. 433,078, filed Oct. 6, 1982, now abandoned,
which in turn was a continuation-in-part application of application
Ser. No. 187,907, filed Sept. 17, 1980, now abandoned, which in
turn was a continuation application of application Ser. No.
008,739, filed Feb. 2, 1979, now abandoned. Patent application Ser.
No. 626,819, filed July 2, 1984, now pending, is a
continuation-in-part of patent application Ser. No. 433,078.
Claims
I claim:
1. A method of preparing an active magnesium hydride which can
reversibly give off and take up H.sub.2, comprising contacting
finely divided magnesium hydride with a solution of a transition
metal organic compound, said transition metal being of Subgroups
IV-VIII of the Periodic Table, and then removing the solution.
2. A method according to claim 1, wherein the contact is effected
in the presence of hydrogen.
3. A method according to claim 1, wherein the transition metal is
selected from the group consisting of titanium, vanadium, chromium,
molybdenum, tungsten, iron, ruthenium, cobalt, rhodium, iridium,
nickel, palladium and platinum.
4. A method according to claim 1, wherein the transition metal
comprises nickel, palladium or iron.
5. A method according to claim 1, wherein the transition metal
organic compound comprises at least one of
bis-(1,5-cyclooctadiene)-nickel (COD.sub.2 Ni), bis-(.eta..sup.3
-allyl)-nickel, bis-(acetylacetonato)-nickel, bis-(ethylato)-nickel
a phosphane-nickel-(O) complex.
6. A method according to claim 1, wherein the transition metal
compound comprises at least one of bis-(.eta..sup.3
-allyl)-palladium, a palladium-phosphane complex, tris-(.eta..sup.3
-allyl)-iron and ferrocene.
7. A method according to claim 1, wherein the solvent of the
solution is selected from the group consisting of an aliphatic
hydrocarbon, an aromatic hydrocarbon, a cycloaliphatic hydrocarbon,
an aliphatic ether, an aromatic ether and a cycloaliphatic aromatic
ether.
8. A method according to claim 1, wherein the contact with the
magnesium hydride is effected at a temperature of about -50.degree.
C. to +150.degree. C.
9. A method according to claim 1, wherein the contact with the
magnesium hydride is maintained for a time sufficient to deposit
the transition metal in from about 0.05 to 20% by weight of the
magnesium.
10. A method according to claim 1, wherein the contact with the
magnesium hydride is maintained for a time sufficient to deposit
the transition metal in from about 1 to 4% by weight of the
magnesium.
11. A method of preparing an active magnesium-hydride, comprising
contacting finely divided metallic magnesium with a solution of a
transition metal-organic compound, said transition metal being of
Subgroups IV-VIII of the Period Table, removing the solvent, and
then contacting the magnesium with hydrogen.
12. A method according to claim 11, wherein the transition metal is
selected from the group consisting of titanium, vanadium, chromium,
molybdenum, tungsten, iron, ruthenium, cobalt, rhodium, iridium,
nickel, palladium and platinum.
13. A method according to claim 11, wherein the transition metal
comprises nickel, palladium or iron.
14. A method according to claim 11, wherein the transition metal
organic compound comprises at least one of
bis-(1,5-cyclooctadiene)-nickel (COD.sub.2 Ni), bis-(.eta..sup.3
-allyl)-nickel, bis-(acetylacetonato)-nickel, bis-(ethylato)-nickel
and a phosphane-nickel-(O) complex.
15. A method according to claim 11, wherein the transition metal
compound comprises at least one of bis-(.eta..sup.3
-allyl)-palladium, a palladium-phosphane complex, tris-(.eta..sup.3
-allyl)-iron and ferrocene.
16. A method according to claim 11, wherein the solvent of the
solution is selected from the group consisting of an aliphatic
hydrocarbon, an aromatic hydrocarbon, a cycloaliphatic hydrocarbon,
an aliphatic ether, an aromatic ether and a cycloaliphatic aromatic
ether.
17. A method according to claim 11, wherein the contact of the
solution with the metallic magnesium is effected at a temperature
of about -50.degree. C. to +150.degree. C.
18. A method according to claim 11, wherein the contact with the
metallic magnesium is maintained for a time sufficient to deposit
the transition metal in from about 0.05 to 20% by weight of the
magnesium.
19. A method according to claim 11, wherein the contact with the
metallic magnesium is maintained for a time sufficient to deposit
the transition metal in from about 1 to 4% by weight of the
magnesium.
Description
The present invention concerns a method of preparing
magnesium-hydride or magnesium systems (MgH.sub.2 --Mg systems)
that can be employed as reversible hydrogen-storage systems.
The MgH.sub.2 --Mg system is the most appropriate of all known
metal-hydride and metal systems that can be used as reversible
hydrogen-storage systems because it has the highest percentage by
weight (7.65% by weight) of reversibly bound hydrogen and hence the
highest energy density (2332 Wh/kg; Reilly & Sandrock, Spektrum
der Wissenschaft, Apr. 1980, 53) per unit of storer.
Although this property and the relatively low price of magnesium
make the MgH.sub.2 --Mg seem the optimum hydrogen storer system for
transportation, for hydrogen-powered vehicles that is, its
unsatisfactory kinetics have prevented it from being used up to the
present time. It is known for instance that pure magnesium can be
hydrogenated only under drastic conditions, and then only very
slowly and incompletely. The dehydrogenation rate of the resulting
hydride is also unacceptable for a hydrogen storer (Genossar &
Rudman, Z. f. Phys. Chem., Neue Folge 116, 215 [1979], and the
literature cited therein).
Intensive efforts have been devoted in recent years to improve the
hydrogenability of magnesium by doping or alloying it with such
individual foreign metals as aluminum (Douglass, Metall. Trans. 6a,
2179 [1975]) indium (Mintz, Gavra, & Hadari, J. Inorg. Nucl.
Chem. 40, 765 [1978]), or iron (Welter & Rudman, Scripta
Metallurgica 16, 285 [1982]), with various foreign metals (German
Offenlegungsschriften 2 846 672 and 2 846 673), or with
intermetallic compounds like Mg.sub.2 Ni or Mg.sub.2 Cu (Wiswall,
Top Appl. Phys. 29, 201 [1978] and Genossar & Rudman, op. cit.)
and LaNi.sub.5 (Tanguy et al., Mater. Res. Bull. 11, 1441
[1976]).
Although these attempts did improve the kinetics, certain essential
disadvantages have not yet been eliminated from the resulting
systems. The preliminary hydrogenation of magnesium doped with a
foreign metal or intermetallic compound still demands drastic
reaction conditions, and the system kinetics will be satisfactory
and the reversible hydrogen content high only after several cycles
of hydrogenation and dehydrogenation. Considerable percentages of
foreign metal or of expensive intermetallic compound are also
necessary to improve kinetic properties. Furthermore, the storage
capacity of such systems are generally far below what would
theoretically be expected for MgH.sub.2.
A considerable advance with respect to the kinetics of MgH.sub.2
--Mg systems is a method, specified in European Pat. No. 0 003 564,
for the homogeneously catalytic hydrogenation of magnesium in which
the magnesium is converted with hydrogen in the presence of a
catalyst consisting of a halide of a metal of Subgroups IV-VIII of
the periodic table and of a magnesium-organic compound or magnesium
hydride, in the presence if necessary of a polycyclic aromatic or
tertiary amine, and in the presence if necessary of a magnesium
halide MgX.sub.2 in which X=Cl, Br, or I.
The main advantage of this method, aside from the mild reaction
conditions accompanying the preliminary hydrogenation of the
magnesium, is the superior kinetics of the resulting system with
respect to the subsequent cycles of dehydrogenation and
hydrogenation. The magnesium can accordingly be charged with
hydrogen during the subsequent dehydrogenation and hydrogenation
cycles either without pressure or under only slightly increased
pressure and at lower temperatures than with known systems of this
type (with the Mg--Mg.sub.2 Ni system for instance). The storage
capacity of an MgH.sub.2 --Mg system obtained by homogeneous
catalysis is also in the vicinity of the theoretical level.
The indicated advantages can be realized with as little as 0.05% of
transition metal by weight of magnesium and beyond 20% little extra
advantage is gained; preferably it ranges from 0.5 to 3%.
Now, a new process that effectively improves the kinetics of
MgH.sub.2 --Mg hydrogen-storer systems has, surprisingly, been
discovered.
The process in accordance with the invention consists of doping a
finely divided form of the magnesium hydride or metallic magnesium
by exposing it to a solution of an appropriate transition-metal
complex or of an appropriate transition-metal organic compound. An
extremely fine distribution of the particular transition metal
precipitates over the surface of the particles of magnesium hydride
or magnesium and assumes the function of catalyst in the
dehydrogenation and hydrogenation cycles.
One particular advantage of the method in accordance with the
invention is that even slight amounts of the precipitated
transition metal provoke a powerful catalytic effect either
immediately or subsequent to only a few cycles of dehydrogenation
and hydrogenation and that this effect is maintained as the cycles
continue. When on the other hand nickel is electrolytically
deposited on magnesium (Eisenberg, Zagnoli, & Sheriden, Journ.
Less Common Metals 74 323 [1980]) for example, its catalytic effect
will decrease precipitously after only a few cycles. Another
advantage is that even though only 3% or less by weight of the
particular transition metal in terms of the magnesium hydride or
magnesium is generally enough to obtain the desired catalytic
effect, the H.sub.2 -storage capacity of the resulting system will
be relatively high.
The elements of Subgroups IV-VII of the periodic table--titanium,
vanadium, chromium, molybdenum, tungsten, iron, ruthenium, cobalt,
rhodium, iridium, nickel, palladium, and platinum--are all
appropriate transition metals.
Complexes or metal-organic compounds of nickel, palladium, and iron
are preferred transition-metal complexes or transition-metal
organic compounds for the method in accordance with the invention.
Especially preferred are bis-(1,5-cyclooctadiene)-nickel (COD.sub.2
Ni), bis-(.eta..sup.3 -allyl)-nickel, bis-(acetylacetonato)-nickel,
bis-(ethylato)-nickel, phosphane-nickel complexes, and
tetracarbonylnickel. When the transition metals palladium and iron
are employed as dopes, they are preferably added in .eta..sup.3
-allyl, .eta..sup.5 -cyclopentadienyl, olefin, phosphane,
acetylacetonato, or carbonyl complexes. Complexes or metal-organic
compounds of platinum, cobalt, rhodium, iridium iron, ruthenium,
chromium, molybdenum, tungsten, titanium, and vanadium can however
also be employed to dope the magnesium or magnesium hydride.
Magnesium hydride obtained by homogeneous catalysis as specified in
the above-mentioned European Pat. No. 0 003 564 (in which the
magnesium is converted with hydrogen in the presence of a catalyst
consisting of a halide of a metal of Subgroups IV-VIII of the
periodic table and of a magnesium-organic compound or magnesium
hydride, in the presence if necessary of a polycyclic aromatic or
tertiary amine, and in the presence if necessary of a magnesium
halide MgX.sub.2 in which X=Cl, Br, or I) is especially appropriate
for doping in accordance with the present invention.
Commercially available magnesium hydride with kinetic properties
made appropriate for dehydrogenation and hydrogenation by doping it
with a transition metal like nickel (Ex. 9) for instance in
accordance with the invention can however also be employed.
The material can be doped in accordance with the invention in an
aliphatic, cycloaliphatic, or aromatic hydrocarbon or in an
aliphatic, cycloaliphatic, or aromatic ether like, for example,
tetrahydrofuran (THF) in which the particular transition-metal
complex or transition-metal organic compound is soluble or partly
soluble. As Example 1 will demonstrate, magnesium hydride obtained
by homogeneous catalysis can be doped in situ with COD.sub.2 Ni in
THF in the presence of the homogeneous hydrogenation catalyst or
subsequent to separation from the catalyst and THF in another
solvent like toluol for example.
The chemical processes basic to the doping method in accordance
with the invention may vary according to dope, solvent, reaction
conditions, and sometimes the presence of hydrogen.
There are four types of doping reaction:
(a) Doping by thermal decomposition of the dissolved
transition-metal complex, occurring for example when the magnesium
hydride is doped with COD.sub.2 Ni in toluene at
100.degree.-110.degree. C. (Ex. 2): ##EQU1## (b) Doping by
hydrogenation of the transition-metal complex: Hydrogen is
introduced (Ex. 9) into the suspension or solution of toluene to
accelerate the doping of MgH.sub.2 with COD.sub.2 Ni in toluene at
20.degree. C. The nickel complex rapidly hydrogenizes
autocatalytically into cyclooctane and nickel that precipitates in
an extremely fine form on the particles of MgH.sub.2 : ##EQU2## If
commercially available metallic-magnesium powder is doped with a
transition metal, the amount of reversibly bound hydrogen will
depend also on the particle size of the powder
Thus, there will be 3.74% by weight of reversibly bound H.sub.2
when 50-mesh magnesium is employed (Ex. 4), whereas, when
fine-grained (325 mesh, Ex. 10) magnesium is employed, a reversible
hydrogen uptake of 6.5% by weight, relatively close to theoretical,
will be attained.
(c) Doping by immediated reaction of the magnesium hydride with the
transition-metal organic compound:
When MgH.sub.2 is doped with bis-(.eta..sup.3 -allyl)-nickel or
bis-(.eta..sup.3 -ally)-palladium in toluene or THF for example,
the transition metal will precipitate even below room temperature,
propene will form, with 70% or more of the propene calculated from
the equations
and
being demonstrable, and the magnesium hydride will
dehydrogenize.
(d) Doping by reducing the transition-metal complex with magnesium
hydride:
When magnesium hydride is doped with nickel(II) complexes like
bis-(acetylacetonato)- or bis-(ethylato)-nickel, it can also be
exploited to reduce the divalent nickel to zero-valent nickel. In
this method, however, a proportion of the magnesium hydride
equivalent to the nickel(II) complex is lost as a storer because of
the formation of the corresponding magnesium salt.
The technical advantages of the improved kinetic properties of
these MgH.sub.2 --Mg hydrogen-storer systems derive from the
hydrogen being charged more rapidly, under lower pressures, and at
lower temperatures and discharged more rapidly and under lower
pressures than was previously possible. This reduces material and
operating costs and makes the hydrogen storers more practical and
reliable to handle.
The accompanying drawings refer together with relevant examples
hereto:
FIG. 1 (Example 1) show hydrogenation-dehydrogenation volume
plotted against time for a sample doped in accordance with the
invention and comparison sample, per Example 1;
FIG. 2 (Example 1) shows a set of curves of hydrogen release volume
at different pressures plotted against temperature, per Example
2;
FIG. 3 (Example 4) shows a comparison of hydrogen release volume at
different times and temperatures for the first 3 cycles comparing a
doped sample in accordance with the invention and an undoped
sample;
FIG. 4 is similar to FIG. 3 (Example 4) for cycles 20-30; and
FIG. 5 is similar to FIG. 3 (Example 4) for cycles 55-58.
The invention will now be specified with reference to the following
examples, without, however, being limited to them in any way.
The appropriateness of the MgH.sub.2 and Mg treated by the methods
specified in the examples for dehydrogenation and hydrogenation
were tested by submitting samples to
(a) one or more cycles of dehydrogenation and hydrogenation under
normal pressure ("normal-pressure test") and
(b) 30-40 or more cycles of dehydrogenation and hydrogenation under
elevated pressure ("high-pressure test") if necessary.
The normal-pressure tests were carried out with a thermovolumetric
apparatus designed for that purpose (Bogdanovic & Spliethoff,
Chem.-Ing.-Tech., 55 (2) 156 1983).
To investigate the properties of the MgH.sub.2 and Mg as H.sub.2
storers over long-term use, the samples were subjected to a series
of dehydrogenation and hydrogenation cycles under slightly elevated
(15 bars max) pressure. A completely automatic and electronically
controlled apparatus developed especially for this purpose was
employed.
The air-sensitive MgH.sub.2 --Mg systems or metal complexes were
tested in argon. The solvents were cleared of air and moisture and
distilled in argon. Technical (99.9%) hydrogen was employed in all
the tests. Fresh hydrogen was always extracted from a cylinder for
the dehydrogenation and hydrogenation cycles.
EXAMPLE 1
15.0 kg (617 moles) of magnesium powder (particle size 0.3 mm, 50
mesh) were hydrogenated into magnesium hydride in 75 l of THF in a
stirrer vessel by the method specified in European Pat. No. 0 003
564 with a titanium catalyst (mole ratio of
Mg:anthracene:TiCl.sub.4 =100:1:1) at 60.degree.-73.degree. C.
under an H.sub.2 pressure of 2 bars.
The H.sub.2 atmosphere of the vessel was replaced with an argon
atmosphere for doping with nickel. 1.4 kg (5 moles) of solid
COD.sub.2 Ni were added to the in situ suspension of MgH.sub.2 in
THF under the argon. The suspension was heated to 100.degree. C.
for 4 hours while stirred. The magnesium hydride, doped with
nickel, was filtered out, washed with THF and pentane, and dried in
a vacuum (0.2-0.4 mbars). The product was subjected to one cycle of
dehydrogenation and hydrogenation (dehydrogenation at
230.degree.-370.degree. C. under 10-0.4 mbars and hydrogenation at
335.degree.-350.degree. C. under 5-10 bars) to clear it of organic
residue. 14.0 kg of magnesium hydride were obtained in the form of
a light gray pyrophoric powder composed of
C 0.0, H 6.01, Mg 85.17, Ti 1.51, Cl 2.72, and Ni 0.89.
Normal-pressure test
A 0.72-g sample of the product was dehydrogenated in a (1-bar)
H.sub.2 atmosphere at 334.degree. C. and then hydrogenated at
230.degree. C. (both temperatures furnace temperatures) in the
thermovolumetric apparatus. Curves b in FIG. 1 represent the
dehydrogenation and hydrogenation cycle.
Curves a in FIG. 1 represent in comparison a dehydrogenation cycle
for a (0.69-g) sample prepared by the same (titanium catalyst)
method but not doped (dehydrogenation at 329.degree. C. under 1 bar
and hydrogenation at 230.degree. C. under 1 bar).
Comparison with the undoped MgH.sub.2 sample shows that doping with
nickel considerably improved not only the dehydrogenation kinetics
but also the hydrogenation of the resulting magnesium. The
dehydrogenation and hydrogenation cycles can be repeated several
times under normal pressure with the doped MgH.sub.2 sample and
will indicate only minimum losses of H.sub.2 -storage capacity.
High-pressure test
A 19.09-g sample of the nickel-doped magnesium hydride was
subjected to a series of 42 dehydrogenation and hydrogenation
cycles at various hydrogenation pressures and time (t.sub.h). The
external dehydrogenation temperature (T.sub.d) was always
367.degree. C. and the external hydrogenation temperature (T.sub.h)
always 267.degree. C. Table I lists the results of the
high-pressure test. FIG. 2, top, illustrates typical curves of
hydrogen release and uptake for cycles carried out under 10, 5, 3,
and 2 bars of H.sub.2 pressure along with the associated
sample-temperature curves. For comparison, a 34-cycle high-pressure
test of a (17.34-g) sample of magnesium hydride prepared with a
titanium catalyst but not doped was carried out under the same
conditions. Table Ia lists the results and FIG. 2, bottom,
illustrates curves for typical cycles.
The results of these two tests reveal that samples of both the
doped and the undoped MgH.sub.2 prepared by homogeneous catalysis
make appropriate reversible hydrogen storers under low H.sub.2
pressures (2-10 bars). Both H.sub.2 -storage capacity and kinetics
remain practically constant subject to measurement error for 42 and
34 cycles under these conditions.
Nevertheless, there were distinct differences in kinetics in favor
of the doped sample (FIG. 2, top and bottom). The hydrogenation
curves for low pressure (2 and 3 bars) reveal the greatest
differences, with the hydrogenation times of the doped samples
being at least 3 times shorter.
The slighter differences in hydrogenation under higher pressures
result from heat transport becoming more and more significant as
the rate-determining factor as hydrogenation becomes more
rapid.
TABLE 1 ______________________________________ Results of
high-pressure test of MgH.sub.2 sample doped with 0.89% nickel (Ex.
1). T.sub.d = 367.degree. C., T.sub.h = 267.degree. C., f.sub.d =
1.5. Dehydrogenation Hydrogenation Cycle H.sub.2 Pressure Time
t.sub.h H.sub.2 No. [l] [bars].sup.a [hours] [l]
______________________________________ 1 13.7 10 2 14.8 2 14.8 " "
" 3 " " " " 4 14.7 " " 14.6 .sup. 5.sup.b 14.6 " " 14.5 6 " " " " 7
" 2 3 14.4 8 14.7 " " " 9 " " " " .sup. 10.sup.b 14.6 " " " 11 " "
" " 12 14.5 5 1.5 " 13 14.7 " " 14.5 14 14.8 " " " .sup. 15.sup.b
14.7 " " " 16 14.6 " " 14.4 17 14.7 3 2 14.5 18 " " " " 19 14.8 " "
" 20 " " " " 21 " " " " 22 14.9 " " " 23 15.0 " " " 24 " " " 14.4
.sup. 25.sup.b " " " 14.5 26 " " " " 27 14.9 " " 14.4 28 15.0 " "
14.5 29 " " " " 30 15.1 " " 14.6 31 15.0 " " 14.7 32 15.1 " " " 33
15.0 " " " 34 " 5 1.5 14.9 35 14.9 " " " 36 " " " 15.0 37 15.0 " "
14.9 38 " " " " 39 14.9 " " " 40 15.1 " " 15.0 41 14.9 " " " 42 " "
" .sup. ".sup.c ______________________________________ .sup.a 0
bars = atmospheric pressure. .sup.b FIG. 2, top illustrates these
cycles. .sup.c Reversible H.sub.2 level after 42 cycles: 6.60% by
weight. Yield: 19.09 g.
TABLE 1a ______________________________________ Results of
high-pressure test of an undoped sample of MgH.sub.2 (Ex. 1).
T.sub.d = 367.degree. C., T.sub.h = 267.degree. C., t.sub.d =
hours. Dehydrogenation Hydrogenation Cycle H.sub.2 Pressure Time
t.sub.h H.sub.2 No. [l] [bars].sup.a [hours] [l]
______________________________________ 1 14.0 10 1 14.3 2 13.6 "
1.5 14.4 3 13.5 " 2 " .sup. 4.sup.b 13.6 " " 14.5 5 " " " " 6 " 5 "
14.0 7 " " " 14.1 .sup. 8.sup.b " " " " 9 13.7 " " 14.0 10 13.6 " "
13.9 11 " " " " 12 " 2 6 13.6 .sup. 13.sup.b 13.3 " " " 14 " " "
13.5 15 13.4 3.5 4.5 14.1 16 13.5 " " " 17 13.4 " " 14.0 18 " " "
13.8 19 " 10 2.5 15.0 20 " 3 5 14.0 21 13.3 " " 13.8 22 13.2 " "
13.6 23 " " " 13.7 24 " " " " 25 13.2 " " 13.6 .sup. 26.sup.b 13.0
" " " 27 " " " 13.8 28 12.9 " " 13.6 29 " " " 13.7 30 " 10 2 .sup.
--.sup.c 31 13.3 " " -- 32 " " " -- 33 " " " -- 34 " " " .sup.
--.sup.d ______________________________________ .sup.a 0 bars =
atmospheric pressure. .sup.b FIG. 2, bottom illustrates these
cycles. .sup.c Not measured. .sup.d Reversible H.sub.2 level after
34 cycles: 6.93% by weight. Yield: 16.13 g.
EXAMPLE 2
218.7 g (0.9 moles) of magnesium powder (particle size 0.3 mm, 50
mesh) were hydrogenated into magnesium hydride in 1.1 l of THF by
the method specified in European Pat. No. 0 003 564 with a chromium
catalyst (mole ratio of Mg:anthracene:CrCl.sub.3 =100:1:1) at
60.degree. C. under a pressure of 20 bars. The product was filtered
out, washed with THF and pentane, and dried in a (0.2-bar) vacuum
at room temperature to constant weight. The yield was 252.2 g of
MgH.sub.2 composed of
C 4.4, H 7.0, Mg 84.2, Cr 0.75 and Cl 2.04%.
Four samples (a-d) weighing 21-23 g of this magnesium hydride were
each suspended in 380 ml of toluene. The toluene suspension was
treated with various amounts of solid COD.sub.2 Ni (Table II). The
batches were then stirred for 15 hours at 100.degree. C. The doped
MgH.sub.2 samples were filtered out, washed with toluene and
pentane, and dried in a (0.2-mbar) vacuum. A sample of undoped
MgH.sub.2 was thermally treated in toluene at 100.degree. C. in the
same way but without the addition of COD.sub.2 Ni.
TABLE 2
__________________________________________________________________________
Doping MgH.sub.2 with COD.sub.2 Ni in toluene at 100.degree. C.
MgH.sub.2 COD.sub.2 Ni Doped MgH.sub.2 Ni %.sup.a Composition of
doped samples [%] Sample [g] [g] [g] calc. Ni C H Mg Cl Cr
__________________________________________________________________________
a 22.4 15.0 20.2 12.5 12.8 6.0 6.1 73.5 0.46 .sup.b b 21.7 3.3 21.6
3.1 3.3 5.6 6.5 83.5 0.42 .sup.b c 21.2 0.74 20.8 0.7 0.8 4.9 6.9
85.4 0.39 .sup.b d 23.0 0.08 22.3 0.07 0.07 4.8 7.0 87.2 0.31
.sup.b
__________________________________________________________________________
.sup.a At 100% doping. .sup.b Not determined.
Normal-pressure test
MgH.sub.2 Samples a-d, doped with nickel, were subjected to the
dehydrogenation and hydrogenation cycle described in Example 1. The
results of the normal-pressure test show that considerable
improvement in hydrogenation kinetics can be achieved even at a
dose of 0.8% nickel (Sample c). Doping with more nickel (Sample a
or b) leads to only inconsiderable further improvement in the
hydrogenation kinetics.
Normal-pressure test at various temperatures
0.79 g of Sample b (with 3.3% nickel) and 0.65 g of Sample e, which
had not been doped with nickel, were dehydrogenated under normal
pressure at 330.degree. C. The resulting samples of "active
magnesium" were hydrogenated at the temperature range of
100.degree.-283.degree. C. and under 1 bar of H.sub.2 pressure. As
the results of this test indicates, both samples can be
hydrogenated at an impressive rate at as low as 150.degree. C.
Hydrogenation rates increase with temperature, reaching a maximum
at 250.degree.-255.degree. C. for both samples. As temperature
continues to rise the hydrogenation rates naturally drop because
the systems are approaching equilibrium (285.degree. C., 1 bar).
Comparison of both samples indicates that the doped sample exhibits
considerably better hydrogenation kinetics throughout the tested
temperature range.
"Ignition tests" were conducted with a nickel-doped sample of
"active magnesium" under various H.sub.2 pressures. Sample b (3.3%
nickel) was dehydrogenated at 330.degree. C. and under 1 bar.
Portions of 11.0 g of the resulting "active magnesium" were
hydrogenated in a 300-ml autoclave at various H.sub.2 pressures.
The autoclave was heated up at a constant rate of 2.degree. C./min
and the temperature inside each sample measured. At pressures of 10
and 15 bars the "ignition temperature" of the sample was about
150.degree. C. During the next 30 minutes the sample heated up
briefly to 380.degree.-390.degree. C. as the result of
hydrogenation heat, and after another 10 minutes the hydrogenation
process was practically complete. At lower H.sub.2 pressures (0.7
and 2 bars) the ignition temperature was naturally higher
(190.degree.-200.degree. C.). A maximum temperature of
270.degree.-290.degree. C. was attained during hydrogenation.
Maximum attainable hydrogenation temperature can, because it can
not exceed the equilibrium temperature corresponding to the H.sub.2
pressure, accordingly be controlled ahead of time by setting a
given H.sub.2 pressure.
EXAMPLE 3
72.3 g (3.0 moles) of powdered magnesium (particle size, 0.3 mm, 50
mesh) were hydrogenated into magnesium hydride in 0.35 l of THF by
the method specified in European Pat. No. 0 003 564 with a titanium
catalyst (mole ratio of Mg:anthracene:TiCl.sub.4 =200:1:1) at
60.degree. C. under a pressure of 80 bars. The product was filtered
out, washed with THF and pentane, and dried in a high vacuum at
room temperature to constant weight. The yield was 252.2 g of a
product composed of
C 3.09, H 7.40, Mg 84.2, Mg 86.86, Ti 0.59, and Cl 1.42% (Sample
f).
An 11.35-g sample of the resulting magnesium hydride was suspended
in 100 ml of toluene. The suspension was treated with 0.90 g of
COD.sub.2 Ni and stirred for 5 hours at 100.degree. C. The doped
magnesium hydride was filtered out, washed with toluene and
pentane, and dried in a high vacuum at room temperature. The yield
was 11.18 g of a product composed of
C 2.90, H 6.79, Mg 86.10, Ni 1.54, Ti 0.59, and Cl 1.01% (Sample
g).
Normal-pressure test
The results of the normal-pressure test show that the doped sample
(Sample g) had considerably better H.sub.2 -storer properties with
respect not only to kinetics but also to reversibility than the
undoped sample (Sample f). Subsequent to 2-3 cycles of
dehydrogenation and hydrogenation the amount of H.sub.2 released at
330.degree. C. had been completely recaptured at 230.degree. C.
EXAMPLE 4
300.0 g (12.3 moles) of powdered magnesium (particle size 0.3 mm,
50 mesh) were heated in a vacuum and suspended in 1 l of toluene.
The suspension was treated with 27.7 g (0.1 mole) of COD.sub.2 Ni.
Hydrogen was introduced at room temperature and under 1 bar into
the yellow toluene solution while stirred and with the magnesium
powder suspended in it until it lost color (about 2 hours). The
doped magnesium powder was filtered out, washed with pentane, and
dried in a vacuum. The yield was 304.2 g of powdered magnesium
doped with 2% nickel.
High-pressure test
A 15.0-g sample of the nickel-doped magnesium powder was subject to
a series of 66 dehydrogenation and hydrogenation cycles varying in
pressure, temperature (T.sub.h), and time (t.sub.h). The autoclave
dehydrogenation temperature (T.sub.d) was always 366.degree. C. and
the dehydrogenation time (t.sub.d) 1 hour. Table 3 shows the
results of the test.
TABLE 3 ______________________________________ Results of
high-pressure test of powdered magnesium sample doped with 2%
nickel. T.sub.d = 366.degree. C., t.sub.d = 1 hour. Hydrogenation
Dehydrog. Cycle T.sub.h Pressure t.sub.h H.sub.2 H.sub.2 No.
[.degree.C.] [bars].sup.a [hours] [l].sup.b [l].sup.b
______________________________________ 1 338 15 9 9.6 8.8 2-4 " " 2
5.4 4.5 5-6 264 " 1 -- " 7-41 338 " " 6.4 5.7 42-54 264 " " 6.1 5.8
55-60 " 5 2 6.5 6.6 61-62 " 15 1 5.6 5.7 63 " " 3 -- 5.8 64-65 338
" 6 8.1 7.6 66 " " 2 6.3.sup.c
______________________________________ .sup.a 0 bars = atmospheric
pressure .sup.b 20.degree. C. under 1 bar .sup.c 15.6 g of
MgH.sub.2 with 3.74% by weight of H.sub.2 weighed out (subsequent
to normalpressure test).
FIG. 3, top, illustrates the course of hydrogenation during the
first three cycles and FIG. 4, top, during dehydrogenation and
hydrogenation cycles 20-23 at a hydrogenation temperature of
338.degree. C. and an H.sub.2 pressure of 15 bars. The two figures
also show the associated sample-temperature curves. FIG. 5, top,
shows the same curves for the same sample during cycles 55-58 at a
hydrogenation temperature of 264.degree. C. and a pressure of 5
bars. For comparison a high-pressure test lasting 31 cycles was
carried out under similar conditions with a 15.1-g sample of
undoped magnesium powder (manufactured by Ventron, 50 mesh). Table
3a and FIGS. 3, 4, and 5, bottom, show the results.
Comparison of the curves in FIGS. 3, 4, and 5, top and bottom,
indicates drastic differences in the kinetic behavior of the two
samples in favor of the nickel-doped sample. These differences are
extremely clear in both the initial (FIG. 3) and subsequent (FIG.
4) dehydrogenation and hydrogenation cycles. Particularly
remarkable differences in hydrogenation kinetics in favor of the
doped sample appear under lower pressures (5 bars, FIG. 5), with
the doped sample exhibiting especially superior kinetics in spite
of the lower external temperature.
TABLE 3a ______________________________________ Results of
high-pressure test of undoped powdered-magnesium sample (Example
4). T.sub.h = 338.degree. C., T.sub.d = 366.degree. C., t.sub.d = 2
hours. Hydrogenation Dehydrog. Cycle Pressure t.sub.h H.sub.2
H.sub.2 No. [bars].sup.a [hours] [l].sup.b [l].sup.b
______________________________________ 1 15 9 -- 0.2 2 " 7 6.2 5.8
3 " 2 4.8 4.9 4 " " 5.5 5.3 5 " " 5.9 5.9 6 " " 6.2 6.4 7 " " 6.4
6.5 8 " " 6.6 6.7 9 5 10 8.0 8.1 10 " " 8.4 8.2 11-31 15 2 7.4-8.1
7.3-8.1 ______________________________________ .sup.a 0 bars =
atmospheric pressure .sup.b 20.degree. C. under 1 bar
EXAMPLE 5
1.79 g of nickel tetracarbonyl in 5 ml of toluene were added to
19.2 g of (undoped) magnesium hydride prepared as in Example 2 in
200 ml of toluene, which was then heated for 8 hours to 100.degree.
C. (reflux coil: acetone and dry ice). The suspension was filtered
and the doped magnesium hydride washed with toluene and pentane and
dried in a vacuum (0.2 mbars). The yield was 20.0 g of a product
composed of
C 6.03, H 6.48, Mg 80.60, Ni 2.60, and Cl 1.11%.
The resulting MgH.sub.2 sample exhibited improved kinetic
properties in the normal-pressure test in comparison with the
undoped sample.
EXAMPLE 6
24.0 g (1.0 moles) of powdered magnesium (particle size: 0.3 mm, 50
mesh) were hydrogenated into magnesium hydride in 150 ml of THF by
the method specified in European Pat. No. 0 003 564 with a chromium
catalyst (mole ratio of Mg:anthracene:CrCl.sub.3 =100:1:1) at
20.degree.-24.degree. C. under a pressure of 80-100 bars. The
product was filtered out, washed with THF and pentane, and dried in
a high vacuum at room temperature to constant weight. The yield was
27.0 g of MgH.sub.2 composed of
C 6.66, H 6.64, Mg 82.64, Cr 1.21 and Cl 2.95% (Sample h).
1.19 g of Sample h were placed in a 25-ml flask connected to a cold
trap and provided with a dropping funnel. The apparatus was
evacuated. A solution of 0.42 g (3.30 mmoles) of bis-(.eta..sup.3
-allyl)-nickel in 4.0 m of toluene was added from the funnel to the
sample while it was being stirred at room temperature. The
resulting gases were condensed in the cold trap (liquid N.sub.2).
After allowing the reaction to occur for 2.5 hours, the cold trap
was defrosted, yielding 60 ml of gas (20.degree. C. and 1 bar)
consisting of 98.5% propene and 1.5% propane (mole %, mass
spectrography). After another 60 hours of reaction at room
temperature the formation of another 43 ml (20.degree. C. and 1
bar) consisting of 95.9% propene and 4.0% propane was demonstrated.
On the whole, 70% of the allyl groups were determined to be
propene, 11.4% propane, and 0.4% hexadiene-1,5 in the reaction of
MgH.sub.2 with bis-(.eta..sup.3 -allyl)-nickel. The solvent
(toluene) was evaporated out in a vacuum and the residue dried in a
high vacuum at room temperature. The product was composed of
C 0.09, H 6.11, Mg 69.94, Ni 12.90, Cr 0.53, and Cl 1.20%.
The resulting nickel-doped MgH.sub.2 sample exhibited improved
kinetic properties in comparison with the undoped sample (Sample h)
in the normal-pressure test.
EXAMPLE 7
1.38 g of the MgH.sub.2 Sample h (Ex. 6) were doped as in Example 6
with 0.39 g (2.1 mmoles) of bis-(.eta..sup.3 -allyl)-palladium at
room temperature. 72.6% of the allyl groups in this reaction were
determined to be propene, 1.2% propane, and 2.4% hexadiene-1,5. The
palladium-doped magnesium hydride was composed of
C 6.34, H 5.90, Mg 72.88, Pd 13.07, Cr 0.47, and Cl 1.13%.
The palladium-doped MgH.sub.2 sample exhibited improved kinetic
properties in comparison with the undoped sample (Sample h) in the
normal-pressure test.
EXAMPLE 8
2.59 g of MgH.sub.2 Sample h (Ex. 6) were suspended in 20 ml of
toluene and treated at -78.degree. C. with a -78.degree. C.
solution of 0.22 g (1.25 mmoles) of tris-(.eta..sup.3 -allyl)-iron
in 20 ml of toluene. The temperature of the mixture was allowed
while stirred to rise from -78.degree. C. to -6.degree. C. within 8
hours. It was then stirred at room temperature for 24 hours. The
iron-doped MgH.sub.2 was filtered out, washed with toluene and
pentane, and dried in a high vacuum. The iron-doped magnesium
hydride was composed of
C 9.45, H 7.13, Mg 78.19, Fe 1.98, Cr 0.45, and Cl 2.56%.
The iron-doped MgH.sub.2 sample exhibited improved kinetic
properties in comparison with the undoped sample (Sample h) in the
normal-pressure test.
EXAMPLE 9
1.86 g (6.8 mmoles) of COD.sub.2 Ni were added to 19.45 g of
magnesium hydride (mf. by Alpha Products) in 100 ml of toluene.
Hydrogen (1 bar) was introduced into the solution or suspension
while the latter was stirred at room temperature. After 630 ml of
H.sub.2 (20.degree. C. and 1 bar), (649 ml calculated for the
hydrogenation of the COD.sub.2 Ni) were taken up within 1.6 hours,
hydrogen takeup was significantly slower. During the next 2.5 hours
230 ml of H.sub.2 (20.degree. C. and 1 bar) were taken up
(hydrogenation of toluene), after which hydrogenation was
interrupted. The suspension was filtered out and the doped
magnesium hydride washed with toluene and pentane and dried in a
high vacuum. The yield was 19.90 g of a product composed of
C 0.39, H 4.95, Mg 84.02, and Ni 1.89%.
The doped MgH.sub.2 sample exhibited considerably improved kinetic
properties in comparison with the undoped sample (from Alpha
Products) in the high-pressure and normal-pressure tests.
EXAMPLE 10
50.0 g (2.06 moles) of powdered magnesium (Alpha Products, 325
mesh) were suspended in 150 m of toluene. The suspension was
treated with 4.77 g (17.4 mmoles) of COD.sub.2 Ni. Hydrogen (1 bar)
was introduced at room temperature from an automatically recording
gas burette (Chem. Ing. Techn., loc. cit.) into the yellow toluene
solution while it was being stirred and with the magnesium powder
suspended in it until there was a sharp kink in the hydrogen-uptake
curve subsequent to the uptake of 1.70 l of H.sub.2 (20.degree. C.
and 1 bar, 102% of th.). Hydrogenation took 1 hour. The doped
magnesium powder was filtered out, washed with pentane, and dried
in a vacuum. The yield was 50.5 g of nickel-doped magnesium
powder.
High-pressure test
A sample of 14.7 g of the resulting magnesium powder was subjected
to a series of 35 hydrogenation and dehydrogenation cycles at
different hydrogenation pressures and times (t.sub.h).
Dehydrogenation autoclave temperature (T.sub.d) was 362.degree. C.
and hydrogenation autoclave temperature (T.sub.h) 264.degree. C.
The dehydrogenation time (t.sub.d) was a constant 1 hour. Except
for the first hydrogenation, which was carried out at 337.degree.
C. and lasted about 4 hours, "effective hydrogenation times" (the
time until the active magnesium practically stopped taking up
H.sub.2) were 1.2 hours at 1 bar, 0.9 hours at 2 bars, 0.8 hours at
3 bars, 0.6 hours at 5 bars, and 0.4 hours at 15 bars (excess
H.sub.2 pressure), with the temperature inside the sample always
increasing to the equilibrium temperature corresponding to the
given H.sub.2 pressure. The effective dehydrogenation times were
0.6 hours, with the temperature inside the sample falling below
300.degree. C. The reversible hydrogen content varied in accordance
with hydrogenation pressure and time during the cycles of
hydrogenation and dehydrogenation between 11.3 l, corresponding to
6.0% by weight, and 12.6 l, corresponding to 6.6% by weight of
MgH.sub.2 (20.degree. C. and 1 bar). A high-pressure test lasting
22 cycles was also conducted under the same conditions with a
sample of 15.0 g of undoped powdered magnesium (Alfa Products, 325
mesh). Comparison of the two tests demonstrated drastic differences
in the kinetic behavior of the two samples in favor of the
nickel-doped sample. The first hydrogenation of the doped sample
was at least 3 times faster and subsequent hydrogenations, at 5 and
3 bars, at least 10 and 15 times faster respectively than the
hydrogenations of the undoped sample. The reversible hydrogen
content of the undoped sample ranged from 6.3 to 6.8% by weight of
MgH.sub.2 in accordance with hydrogenation pressure and time.
It will be understood that the specification and examples are
illustrative but not limitative of the present invention and that
other embodiments within the spirit and scope of the invention will
suggest themselves to those skilled in the art.
* * * * *